This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. In the human, mouse and cattle genomes, there is a contiguous region encoding multiple copies of Bactericidal/Permeability Increasing Protein- like proteins (BPI-like proteins). These proteins are thought to play diverse roles in the innate host-defense response in mammals. In cattle, there are 13 homologues encoded on a 722 kb contiguous region and these represent an expansion of this family compared to humans and mouse (which encode 9 and 11 homologues respectively). We have focused on one of these BPI-like genes, BSP30b, which is the major protein component in the saliva of cattle and is most closely related to the parotid secretory protein (PSP) in mouse and human. It is thought that BSP30b may be responsible for innate protection in the oral cavity of ruminants or, alternatively, may play an important role in the rumen where there exists a very complex anaerobic community of microbes involved in the degradation of plant matter. Elucidation of the structure of BSP30b will show the possible binding site for hydrophobic ligands and give clues to the possible role for this important and abundant protein.